Apparatus and Method for Terminating Probe Apparatus of Semiconductor Wafer

ABSTRACT

A method and apparatus for terminating a probe that probes a semiconductor device with a signal cable from a tester is provided to connect layers of the probe to layers of the signal cable side by side. The probe and signal cable can be a co-axial or tri-axial probe and signal cable, respectively. A center conductive probe needle of the probe is disposed side by side with and electrically connects to a center signal conductor of the signal cable. A dielectric layer of the probe is disposed side by side with and connects to a dielectric layer of the signal cable. A conductive guard layer of the probe is disposed side by side with and electrically connects to a conductive dispersion/guard layer of the signal cable, and a sleeve of the probe is disposed side by side with and connects to a sleeve of the signal cable. In a tri-axial embodiment, a second dielectric layer of the probe is disposed side by side with and connects to a second dielectric layer of the signal cable.

CROSS-REFERENCE TO RELATED APPLICATION

None.

FIELD OF THE INVENTION

The present invention relates generally to semiconductor test equipment,and more particularly, to a probe apparatus used in semiconductor testequipment for electrically probing devices on a semiconductor wafer.

BACKGROUND OF THE INVENTION

The semiconductor industry has a need to access many electronic deviceson a semiconductor wafer. As the semiconductor industry grows anddevices become more complex, many electrical devices, most commonlysemiconductor devices, must be electrically tested, for example, forleakage currents and extremely low operating currents. These currentsare often below 100 fA. In addition, the currents and devicecharacteristics are often required to be evaluated over a widetemperature range to understand how temperature affects a device. Also,because of materials characteristics of dielectrics, it is oftendifficult to test characteristics of semiconductor devices in a wideoperating temperature range.

To effectively measure at currents below 100 fA (Femto Ampere), ameasurement signal must be isolated from external electricalinterference, leakage currents through the dielectric material,parasitic capacitance, triboelectric noise, piezoelectric noise, anddielectric absorption, etc.

Accordingly, there is a need for improved semiconductor test equipmentfor electrically probing semiconductor devices at low currents over awide temperature range.

SUMMARY OF THE INVENTION

To solve the above and the other problems, the present inventionprovides a probe apparatus having a probe that probes a semiconductordevice and terminates with a signal cable side by side. In oneembodiment, the apparatus includes at least one layer of a probe and atleast one layer of the signal cable connected side by side.

In one embodiment of the present invention, the probe apparatusincludes: a chassis; a dielectric block mounted in the chassis forretaining the probe, the probe extending on the chassis from a proximalend of the probe to the dielectric block, extending through thedielectric block, and projecting from the dielectric block towards thesemiconductor device at a distal end of the probe; and a terminatingdevice, mounted on the chassis or dielectric block, for terminating theproximal end of the probe with a distal end of the signal cable side byside.

In one embodiment of the probe apparatus of the present invention, theprobe is a co-axial shielded probe which includes: a center conductiveprobe needle; a dielectric layer surrounding the center conductive probeneedle; a conductive guard layer surrounding the dielectric layer; and anon-conductive sleeve which may be beat shrinkable surrounding theconductive guard layer. The signal cable is a co-axial signal cablewhich includes: a center signal conductor; a dielectric layersurrounding the center signal conductor; a conductive dispersion/guardlayer surrounding the dielectric layer; and a non-conductive sleevewhich may be heat shrinkable surrounding the conductive dispersion/guardlayer. The center conductive probe needle of the shielded probe isdisposed side by side with and electrically connects to the centersignal conductor of the signal cable. The dielectric layer of theshielded probe is disposed side by side with and connects to thedielectric layer of the signal cable. The conductive guard layer of theshielded probe is disposed side by side with and electrically connectsto the conductive dispersion/guard layer of the signal cable. The sleeveof the shielded probe is disposed side by side with and connects to thesleeve of the signal cable.

In an alternative embodiment, the probe is a tri-axial shielded probewhich additionally includes a second dielectric layer and a secondconductive layer sandwiched between the conductive guard layer and thesleeve of the co-axial shielded probe, and the signal cable is atri-axial cable which additionally includes a second dielectric layerand a second conductive layer sandwiched between the conductivedispersion/guard layer and the sleeve of the co-axial signal cable. Thesecond dielectric layer of the shielded probe is disposed side by sidewith and connects to the second dielectric layer of the signal cable.The second conductive layer of the shielded probe is disposed side byside with and electrically connects to the second conductive layer ofthe signal cable.

Still in one embodiment of the probe apparatus of the present invention,the terminating device includes a shrink tube for shrink-tubing thesleeve of the shielded probe and the sleeve of the signal cabletogether, for shrink-tubing the conductive guard layer of the shieldedprobe and the conductive dispersion/guard layer of the signal cabletogether, for shrink-tubing the dielectric layer of the shielded probeand the dielectric layer of the signal cable together, and forshrink-tubing the center conductive probe needle of the shielded probeand the center signal conductor of the signal cable together. In thealternative embodiment, the shrink tube shrink-tubes the seconddielectric layer of the shielded probe and the second dielectric layerof the signal cable together.

Additionally in one embodiment of the present invention, the probeapparatus includes a plate disposed on bottom of the chassis and a coverdisposed on top of the chassis. The plate, the chassis, and the coverare made of metal. The plate is electrically isolated from the chassisby a dielectric spacer and separately biased to reduce or minimizeparasitic capacitance between the chassis and the semiconductor device.The plate is also a heat shield between the semiconductor device and thechassis to improve test performance and mechanical stability. The coverprotects the probe apparatus from mechanical damage contamination,light, and electrical magnetic interference (“EMI”) that could disruptlow current measurements, such as measurements below 100 fA.

Further in one embodiment of the present invention, the dielectric blockis made of ceramic materials. The dielectric block includes a conduit toretain the shielded probe. The dielectric block may include multiplesites for receiving multiple probes.

Furthermore in one embodiment of the present invention, the probeapparatus includes a purge port disposed on the chassis and a purge tubeinserted in the purge port to provide dry air, such as inert gas, in theprobe apparatus.

These and other advantages of the present invention will become apparentto those skilled in the art from the following detailed description,wherein it is shown and described illustrative embodiments of theinvention, including best modes contemplated for carrying out theinvention. As it will be realized, the invention is capable ofmodifications in various obvious aspects, all without departing from thespirit and scope of the present invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a probe apparatus for probing asemiconductor device, in accordance with the principles of the presentinvention.

FIG. 2 is an exploded view of a probe apparatus having a cover, chassis,and plate, with shielded probes and signal cables being removed, inaccordance with the principles of the present invention.

FIG. 3 is a top plan view of the chassis of the probe apparatus with theshielded probes and the signal cables terminated on the chassis, inaccordance with the principles of the present invention.

FIG. 4 is an enlarged perspective view of the shielded probes beinginserted into a dielectric block and terminated with the signal cablesat a terminating device, in accordance with the principles of thepresent invention.

FIG. 5 is an enlarged bottom view of the plate of the probe apparatuswith a plurality of probe needles of the shielded probes, in accordancewith the principles of the present invention.

FIG. 6 is a perspective view of the probe apparatus having a co-axialshielded probe terminating with a co-axial signal cable at a terminatingdevice, in accordance with the principles of the present invention.

FIG. 7 is a perspective view of the probe apparatus having a tri-axialshielded probe terminating with a tri-axial signal cable at aterminating device, in accordance with the principles of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of a preferred embodiment, reference ismade to the accompanying drawings, which form a part hereof, and inwhich is shown by way of illustration a specific embodiment in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

For purposes of explanation, numerous specific details are set forth inthe following description in order to provide a thorough understandingof the present invention. However, it will be evident to one of ordinaryskill in the art that the present invention may be practiced withoutsome of these specific details.

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetailed preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiment illustrated.

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiments, wherein these innovative teachings are advantageouslyapplied to the particular problems of a probe apparatus or probe cardfor measuring low currents with a wide operating temperature range inprobing a semiconductor device. However, it should be understood thatthese embodiments are only examples of the many advantageous uses of theinnovative teachings herein. In general, statements made in thespecification of the present application do not necessarily limit any ofthe various claimed inventions. Moreover, some statements may apply tosome inventive features but not to others. In general, unless otherwiseindicated, singular elements may be in the plural and visa versa with noloss of generality.

The following terms are particularly described throughout thedescription:

Semiconductor Device Not Limitive

The present invention is particularly suitable for probing semiconductordevices, but the use of the present teachings is not limited to probingsemiconductor devices. Other devices may be applied to the presentinvention teachings. Thus, while this specification speaks in terms ofprobing ‘semiconductor’ devices, this term should be interpreted broadlyto include probing any suitable device.

Low Current Not Limitive

The present invention solves the problem of measuring currents below 100fA, but the current range of the present teachings is not limited tobelow 100 fA. For example, the present invention may be applied tomeasure the currents at or above 100 fA in a semiconductor device. Thus,while this specification speaks in terms of ‘low currents’ or ‘measuringcurrents below 100 fA’, these terms should be interpreted broadly toinclude any current that flows through a semiconductor device whichcould be at or above 100 fA.

Wide Temperature Not Limitive

The present invention solves the problem of measuring currents of asemiconductor device in a narrow or limited operating temperature range.The present teachings do not limit to a specific operating temperaturerange. The present application allows a tester to electrically probesemiconductor devices over a wide operating temperature range, not onlyat a low operating temperature but also a high operating temperature,e.g. an operating temperature up to 300 C and beyond. Thus, while thisspecification speaks in terms of ‘wide temperature range’ or ‘measuringcurrents in a wide operating temperature range’, these terms should beinterpreted broadly to include any suitable operating or testingtemperature range of a semiconductor device.

Probe Not Limitive

The present invention solves the problem of measuring currents of asemiconductor device using a co-axial or a tri-axial shielded probe.However, nothing in the teachings of the present invention limitsapplication of the teachings of the present invention to a probe withmore or less layers. Advantageous use of the teachings of the presentinvention may be had with a probe of any number of layers.

Signal Cable Not Limitive

The present invention solves the problem of measuring currents of asemiconductor device using a co-axial or a tri-axial signal cable.However, nothing in the teachings of the present invention limitsapplication of the teachings of the present invention to a signal cablewith more or less layers. Advantageous use of the teachings of thepresent invention may be had with a signal cable of any number oflayers.

Terminating Device Not Limitive

One skilled in the art will readily realize that the present inventionis not limited in scope to a particular terminating device forterminating a probe and a signal cable, such as side by side, or in aswitch configuration type, etc. Furthermore, the present invention isnot limited to how the terminating device is secured to a chassis of theprobe apparatus.

Heat Shrinkable Sleeve and Shrink Tube Method Not Limitive

One skilled in the art will readily realize that the present inventionis not limited in scope to a particular method of connecting a signalcable to a shielded probe, for example shrink-tubing, crimping, orclamping, to electrically connect the center conductive probe needle ofthe shielded probe to the center conductor of the signal cable, toconnect the dielectric layer of the shielded probe to the dielectriclayer of the signal cable, to electrically connect the guard layer ofthe shielded probe to the guard layer of the signal cable, and to heatshrink the sleeve of the shielded probe to the sleeve of the signalcable.

Metals Not Limitive

Throughout the discussion herein there will be examples provided thatmake reference to metals in regards to chassis, cover, and plate. Thepresent invention does not recognize any limitations in regards to whattypes of metals may be used in affecting the teachings of the presentinvention. One skilled in the art will recognize that any conductiveinterconnecting material may be used with no loss of generality inimplementing the teachings of the present invention.

Ceramic Not Limitive

Throughout the discussion herein there will be examples provided thatmake reference to ceramic in regards to dielectric block or tile. Thepresent invention does not recognize any limitations in regards to whattypes of ceramic may be used in affecting the teachings of the presentinvention. One skilled in the art will recognize that anynon-conductive, highly heat-resistant material may be used with no lossof generality in implementing the teachings of the present invention.

Exemplary Embodiment

As shown in FIG. 1, a probe apparatus 100 of the present invention has aplurality of input and output signal cables 102 . The signal cables 102are attached to a connector 104 that is connected to a test equipment(not shown). The test equipment sends probing signals to a semiconductordevice (not shown) via the signal cables 102 and the probe apparatus100, and/or receives tested signals from the semiconductor device viathe probe apparatus 100 and the signal cables 102.

The probe apparatus 100 may include a view port 106. Through the viewport 106, a plurality of probes 108 and bond pads 110 (see FIG. 6) canbe viewed. The description of probes, bond pads, ceramic tiles, andconfigurations of a probe card apparatus are disclosed in a pendingutility patent application, Ser. No. 09/730,130, filed Dec. 4, 2000,which is a Continuation-In-Part (“CIP”) patent application, Ser. No.09/021,631, filed Feb. 10, 1998, which are incorporated herewith byreference.

FIG. 2 illustrates the probe apparatus 100 having a cover 112, a chassis114, and a plate 116, wherein probes and signal cables are removed. Thechassis 114 is made of metal, for example, aluminum or stainless steelor a nickel alloy, etc. The chassis 114 is covered between the cover 112and the plate 116 both made of metal. The plate 116 is electricallyisolated from the chassis 114 by a plurality of dielectric spacers 118and separately biased to reduce or minimize parasitic capacitancebetween the chassis 114 and a semiconductor wafer or chuck (not shown).A coaxial connection 120 is provided to individually bias the plate 116with a voltage potential equal to that of a guard on a semiconductorwafer or chuck (not shown), and the chassis 114 is grounded by a groundcable 122, such that the plate 116 provides a parasitic capacitanceshield for the semiconductor device under test. The plate 116 and thedielectric spacers 118 also form a heat shield to isolate thesemiconductor device and the chassis 114 from external heat therebysignificantly improving test performance.

A plurality of screws 124, such as flat head cap screws, may be includedto fasten the cover 112, the chassis 114, the plate 116, and thedielectric spacers 118 together.

The cover 112 is disposed on top of the chassis 114. The cover 112protects the probe apparatus 100 from mechanical damage contamination,light, and electrical magnetic interference (“EMI”) that could disruptlow current measurements, such as measurements below 100 fA.

FIGS. 3-4 illustrate the chassis 114 of the probe apparatus 100 with theprobes 108 and the signal cables 102 terminated by a terminating device132 on the chassis 114. The probe 108 probes a semiconductor device (notshown) at a distal end 126 of the probe 108 and terminates with thesignal cable 102 at a proximal end 128 of the probe 108. The probeapparatus 100 includes a dielectric block 130 mounted in the chassis 114for retaining the probe 108. The probe 108 extends on the chassis 114from the proximal end 128 of the probe 108 to the dielectric block 130,extending through the dielectric block 130 and projecting from thedielectric block 130 towards the semiconductor device at the distal end126 of the probe 108.

The terminating device 132 is mounted on the chassis 114 for terminatingthe proximal end 128 of the probe 108 with a distal end 134 of thesignal cable 102 side by side. As shown in FIGS. 3 and 4, theterminating device 132 includes a screw 142 and a strain relief 144. Thescrew 142, such as a pan head screw, may be included to hold the strainrelief 144 onto the chassis 114 in place. The strain relief 144 is madeof silicon rubber sheet or the like. A shrink-tube 162 is disposedinside the strain relief 144 to shrink-tube the proximal end 128 of theprobe 108 and the distal end 134 of the signal cable 102 side by sidetogether.

Also shown in FIG. 3, a cavity 136 disposed on the chassis 114 may beincluded to hold the signal cable 102 in place with a cable strainrelief (not shown) Further, a purge tube 140 may be inserted through thecable strain relief into the chassis 114 to provide dry air, such asinert gas, e.g. dry nitrogen, in the probe apparatus 100.

Also shown in FIG. 4, a glass lens 138 may be mounted on the dielectricblock 130 to cover the view hole 106 so as to keep the dry air fromflowing into a probe test area. Thus, the operating temperature in theprobe test area is not affected by the dry air which is typically in acold temperature.

FIG. 5 illustrates a bottom plan view of the plate 116 of the probeapparatus 100 with a plurality of probe needles 146 of the probes 108extending out of the dielectric block. The details of how the probesextend in, through, and out of the dielectric block are disclosed in apending utility patent application, Ser. No. 09/730,130, filed Dec. 4,2000, which is a Continuation-In-Part (“CIP”) patent application, Ser.No. 09/021,631, filed Feb. 10, 1998, which are incorporated herewith byreference.

In the embodiments of the probe apparatus 100 as shown in FIGS. 3 and 4,the probe 108 can be a co-axial probe or a tri-axial probe, and thesignal cable 102 can be a co-axial signal cable or a tri-axial signalcable. It will be appreciated that the probe and the signal cable mayinclude additional layers without departing from the principles of thepresent invention.

FIG. 6 illustrates the probe apparatus 100 having a co-axial shieldedprobe 108 a terminating with a co-axial signal cable 102 a at theterminating device 132. The shielded probe 108 a includes a centerconductive probe needle 146 a, a dielectric layer 148 a surrounding thecenter conductive probe needle 146 a, a conductive guard layer 150 asurrounding the dielectric layer 148 a, a non-conductive heat-shrinkablesleeve 152 a surrounding the conductive guard layer 150 a. The signalcable 102 a includes a center signal conductor 154 a, a dielectric layer156 a surrounding the center signal conductor 154 a, a conductivedispersion/guard layer 158 a surrounding the dielectric layer 156 a, anda non-conductive heat-shrinkable sleeve 160 a surrounding the conductivedispersion/guard layer 158 a.

At a distal end 126 a, the shielded probe 108 a extends from thedielectric block 130 toward the bond pad 110. The sleeve 152 a isremoved when it is inserted into the dielectric block 130.

As shown in FIG. 6, at the proximal end 128 a, the center conductiveprobe needle 146 a of the shielded probe 108 a is disposed side by sidewith and electrically connects to the center signal conductor 154 a ofthe signal cable 102 a. The dielectric layer 148 a of the shielded probe108 a is disposed side by side with and connects to the dielectric layer156 a of the signal cable 102 a. The conductive guard layer 150 a of theshielded probe 108 a is disposed side by side with and electricallyconnects to the conductive dispersion/guard layer 158 a of the signalcable 102 a. The sleeve 152 a of the shielded probe 108 a is disposedside by side with and connects to the sleeve 160 a of the signal cable102 a.

As shown in FIG. 6, the terminating device 132 includes a shrink tube162 a for shrink-tubing the sleeve 152 a of the shielded probe 108 a andthe sleeve 160 a of the signal cable 102 a together, for shrink-tubingthe conductive guard layer 150 a of the shielded probe 108 a and theconductive dispersion/guard layer 158 a of the signal cable 102 atogether, for shrink-tubing the dielectric layer 148 a of the shieldedprobe 108 a and the dielectric layer 156 a of the signal cable 102 atogether, and for shrink-tubing the center conductive probe needle 146 aof the shielded probe 108 a and the center signal conductor 154 a of thesignal cable 102 a together. The shrink tube 162 a is covered by thestrain relief 144 a.

An extension 164 a of the shrink tube 162 a is disposed at an end of thecenter conductive probe needle 146 a and the center signal conductor 154a, and is configured sufficiently wide enough to prevent electricalcurrent from leaking from the center conductive probe needle 146 a andthe center signal conductor 154 a to the strain relief 144 a. Inaddition, the center conductive probe needle 146 a and the center signalconductor 154 a may be soldered, brazed, welded, crimped, or snuggledtherebetween at 166 a to provide additional clearance between the centerconductive probe needle 146 a and the strain relief 144 a, andadditional clearance between the center signal conductor 154 a and thestrain relief 144 a.

FIG. 7 illustrates the probe apparatus 100 having a tri-axial shieldedprobe 108 b terminating with a tri-axial signal cable 102 b at theterminating device 132. The tri-axial shielded probe 108 b additionallyincludes a second dielectric layer 168 sandwiched between a conductiveguard layer 150 b and the sleeve 152 b. A guard layer 169 may beincluded between the second dielectric layer 168 and the sleeve 152 b.The signal cable 102 b additionally includes a second dielectric layer170 sandwiched between the conductive dispersion/guard layer 158 b andthe sleeve 160 b. A guard layer 171 may be included between the seconddielectric layer 171 and the sleeve 160 b. Accordingly, as shown in FIG.7, the shielded probe 108 b includes a center conductive probe needle146 b, a dielectric layer 148 b surrounding the center conductive probeneedle 146 b, the conductive guard layer 150 b surrounding thedielectric layer 148 b, the second dielectric layer 168 surrounding theconductive guard layer 150 b, the guard layer 169 surrounding the seconddielectric layer 168, and the sleeve 152 b surrounding the guard layer169. The signal cable 102 b includes a center signal conductor 154 b, adielectric layer 156 b surrounding the center signal conductor 154 b,the conductive dispersion/guard layer 158 b surrounding the dielectriclayer 156 b, the second dielectric layer 170 surrounding the conductivedispersion/guard layer 158 b, the guard layer 171 surround the seconddielectric layer 170, and the sleeve 160 b surrounding the guard layer171.

At a distal end 126 b, the shielded probe 108 b extends from thedielectric block 130 toward the bond pad 110. The sleeve 152 b isremoved when it is inserted into the dielectric block 130.

As shown in FIG. 7, at the proximal end 128 b, the center conductiveprobe needle 146 b of the shielded probe 108 b is disposed side by sidewith and electrically connects to the center signal conductor 154b ofthe signal cable 102 b. The dielectric layer 148 b of the shielded probe108 b is disposed side by side with and connects to the dielectric layer156 b of the signal cable 102 b. The conductive guard layer 150 b of theshielded probe 108 b is disposed side by side with and electricallyconnects to the conductive dispersion/guard layer 158 b of the signalcable 102 b. The second dielectric layer 168 of the shielded probe 108 bis disposed side by side with and connects to the second dielectriclayer 170 of the signal cable 102 b. The guard layer 169 of the shieldedprobe 108 b is disposed side by side with and electrically connects tothe guard layer 171 of the signal cable 102 b. The sleeve 150 b of theshielded probe 108 b is disposed side by side with and connects to thesleeve 160 b of the signal cable 102 b. As shown in FIG. 7, theterminating device 132 includes a shrink tube 162 b for shrink-tubingthe sleeve 152 b of the shielded probe 108 b and the sleeve 160 b of thesignal cable 102 b together, for shrink-tubing the second dielectriclayer 168 of the shielded probe 108 b and the second dielectric layer170 of the signal cable 102 b together, for shrink-tubing the conductiveguard layer 150 b of the shielded probe 108 b and the conductivedispersion/guard layer 158 b of the signal cable 102 b together, forshrink-tubing the guard layer 169 of the shielded probe and the guardlayer 171 of the signal cable 102 b, for shrink-tubing the dielectriclayer 148 b of the shielded probe 108 b and the dielectric layer 156 bof the signal cable 102 b together, and for shrink-tubing the centerconductive probe needle 146 b of the shielded probe 108 b and the centersignal conductor 154 b of the signal cable 102 b together. The shrinktube 162 b is covered by the strain relief 144 b.

An extension 164 b of the shrink tube 162 b is disposed at an end of thecenter conductive probe needle 146 b and the center signal conductor 154b, and is configured sufficiently wide enough to prevent electricalcurrent from leaking from the center conductive probe needle 146 b andthe center signal conductor 154 b to the strain relief 144 b. Inaddition, the center conductive probe needle 146 b and the center signalconductor 154 b may be soldered, brazed, welded, crimped, or snuggledtherebetween at 166 b to provide additional clearance between the centerconductive probe needle 146 a and the strain relief 144 b, andadditional clearance between the center signal conductor 154 a and thestrain relief 144 b.

The probe needle is preferably made of metal, such as Tungsten (W). Thedielectric layer is preferably a high operating temperature polymer. Theshrink-tube is preferably made of PTFE materials. The dielectric blockis preferably made of ceramic materials and may include multiple sitesfor receiving multiple probes. The dielectric block may or may not haveopenings to view the tips of probe needles.

As described above, each probe is attached to a high operatingtemperature, low triboelectric noise signal cable to facilitateconnection to electronic testing and equipment measurement. To terminatethe probe apparatus 100, the signal cable is connected to the probe bystripping back the sleeves of the probe and signal cable, placing theproximal end of the probe along side the distal end of the signal cableand shrinking the sleeves. Crimping and/or clamping methods can also beused to terminate the signal cable with the probe. Ultra hightemperature solders may be added between the end of the center signalconductor and the end of the probe needle to firmly join the ends.Alternatively, the probe needle can be brazed onto the center signalconductor to join the ends.

In one embodiment of the dispersion/guard layer of the signal cable, aguard braid covers the entire dispersion layer of the signal cable. Inan alternative embodiment, a guard braid is peeled back and partiallyremoved to expose the conductive dispersion/guard layer of the signalcable. The conductive dispersion/guard layer is held against theconductive guard braid of the probe by the force of the shrink tube,thereby eliminating the possibility of the guard braid piercing theprobe's conductive guard layer and the polymer-coated dielectric layerand creating an electrical short circuit between the center conductiveprobe needle and the conductive guard layer of the probe

The shrink-tube assembly is encased in the protective strain relief andanchored to the chassis. The protective strain relief is preferably asilicone rubber tube. The shrink tube is surrounded by the strainrelief. The strain relief and the shrink tube are slipped over thesleeves of the probe and signal cable to suspend the unguarded butshrink-tubed tips of the probe and signal cable in air, therebyeliminating any current leakage paths. The signal cables for each probeneedle are then routed outside the chassis through a second strainrelief mounted on the chassis. The coaxial or tri-axial signal cablewith the sleeve extended into the chassis can also be used to reducecross talk.

The conductive metal cover is placed on the metal chassis to protect andshield the assembly from mechanical damage contamination, light, andelectromagnetic interference (“EMI”) that could disrupt the low currentmeasurements. An electrically isolated plate is placed on the bottom ofthe chassis and separately biased to reduce or minimize any parasiticcapacitance of the probe apparatus.

From the above description and drawings, it will be understood by thoseof ordinary skill in the art that the particular embodiments shown anddescribed are for purposes of illustration only and are not intended tolimit the scope of the present invention. Those of ordinary skill in theart will recognize that the present invention may be embodied in otherspecific forms without departing from its spirit or essentialcharacteristics. References to details of particular embodiments are notintended to limit the scope of the invention.

1. A probe apparatus having a probe that probes a semiconductor deviceand terminates with a signal cable from a tester, comprising: a chassis;a dielectric block mounted in the chassis for retaining the probe, theprobe extending on the chassis and projecting from the dielectric blocktowards the semiconductor device at a distal end of the probe; and aterminating device mounted on the chassis for terminating the proximalend of the probe with a distal end of the signal cable side by side. 2.The apparatus of claim 1, wherein the probe is a co-axial shielded probewhich comprises: a center conductive probe needle; a dielectric layersurrounding the center conductive probe needle; a conductive guard layersurrounding the dielectric layer; and a sleeve surrounding theconductive guard layer.
 3. The apparatus of claim 2, wherein the signalcable is a co-axial signal cable which comprises: a center signalconductor; a dielectric layer surrounding the center signal conductor; aconductive dispersion/guard layer surrounding the dielectric layer; anda sleeve surrounding the conductive dispersion/guard layer.
 4. Theapparatus of claim 3, wherein the center conductive probe needle of theshielded probe is disposed side by side with and electrically connectsto the center signal conductor of the signal cable, the dielectric layerof the shielded probe is disposed side by side with and connects to thedielectric layer of the signal cable, the conductive guard layer of theshielded probe is disposed side by side with and electrically connectsto the conductive dispersion/guard layer of the signal cable, and thesleeve of the shielded probe is disposed side by side with and connectsto the sleeve of the signal cable.
 5. The apparatus of claim 1, whereinthe probe is a tri-axial shielded probe which comprises: a centerconductive probe needle; a dielectric layer surrounding the centerconductive probe needle; a conductive guard layer surrounding thedielectric layer; a second dielectric layer surrounding the conductiveguard layer; a guard layer surrounding the second dielectric layer; anda sleeve surrounding the guard layer.
 6. The apparatus of claim 5,wherein the signal cable is a tri-axial signal cable which comprises: acenter signal conductor; a dielectric layer surrounding the centersignal conductor; a conductive dispersion/guard layer surrounding thedielectric layer; a second dielectric layer surrounding the conductivedispersion/guard layer; a guard layer surrounding the second dielectriclayer; and a sleeve surrounding the guard layer.
 7. The apparatus ofclaim 6, wherein the center conductive probe needle of the shieldedprobe is disposed side by side with and electrically connects to thecenter signal conductor of the signal cable, the dielectric layer of theshielded probe is disposed side by side with and connects to thedielectric layer of the signal cable, the conductive guard layer of theshielded probe is disposed side by side with and electrically connectsto the conductive dispersion/guard layer of the signal cable, the seconddielectric layer of the shielded probe is disposed side by side with andconnects to the second dielectric layer of the signal cable, the guardlayer of the shielded probe is disposed side by side with andelectrically connects to the guard layer of the signal cable; and thesleeve of the shielded probe is disposed side by side with and connectsto the sleeve of the signal cable.
 8. The apparatus of claim 4, whereinthe terminating device comprises a shrink tube for shrink-tubing theshielded probe and the signal cable.
 9. The apparatus of claim 7,wherein the terminating device comprises a shrink tube for shrink-tubingthe shielded probe and the signal cable.
 10. The apparatus of claim 1,further comprising: a plate disposed on bottom of the chassis; a coverdisposed on top of the chassis; a dielectric spacer disposed between thechassis and the plate such that the plate is electrically isolated fromthe chassis and separately biased to minimize parasitic capacitancebetween the chassis and the semiconductor device.
 11. The apparatus ofclaim 10, wherein the plate is a heat shield for the semiconductordevice and the chassis to improve test performance, and the cover is ashield for protecting the probe apparatus from interference that coulddisrupt measurements below 100 fA.
 12. The apparatus of claim 1, whereinthe dielectric block is made of ceramic which comprises a conduit toretain the probe.
 13. The apparatus of claim 12, wherein the dielectricblock comprises a plurality of sites for receiving a plurality ofprobes.
 14. The apparatus of claim 12, further comprising: a purge tubeinserted into the chassis to provide purge air in the probe apparatus.15. The apparatus of claim 14, further comprising a glass lens mountedon the dielectric block to prevent the purge air from cooling thesemiconductor device.
 16. A method of terminating a probe that probes asemiconductor device with a signal cable, comprising the steps of:stripping back at least one layer of the signal cable and at least onelayer of the probe; placing a proximal end of the probe along side of adistal end of the signal cable; and shrinking the at least one layer ofthe signal cable and the at least one layer of the probe.
 17. The methodof claim 16, wherein the step of placing the proximal end of the probealong side of the distal end of the signal cable comprises the steps of:placing a center conductive probe needle of the probe side by side withand electrically connected to a center signal conductor of the signalcable; placing a dielectric layer of the probe side by side with andconnected to a dielectric layer of the signal cable; placing aconductive guard layer of the probe side by side with and electricallyconnected to a conductive dispersion/guard layer of the signal cable;and placing a sleeve of the probe side by side with and connected to asleeve of the signal cable.
 18. The method of claim 16, wherein the stepof placing the proximal end of the probe along side of the distal end ofthe signal cable comprises the steps of: placing a center conductiveprobe needle of the probe side by side with and electrically connectedto a center signal conductor of the signal cable; placing a dielectriclayer of the probe side by side with and connected to a dielectric layerof the signal cable; placing a conductive guard layer of the probe sideby side with and electrically connected to a conductive dispersion/guardlayer of the signal cable; placing a second dielectric layer of theprobe side by side with and connected to a second dielectric layer ofthe signal cable; and placing a sleeve of the probe side by side withand connected to a sleeve of the signal cable.
 19. An apparatus forterminating a probe that probes a semiconductor device with a signalcable, the apparatus comprising at least one layer of the probe and atleast one layer of the signal cable connected side by side.
 20. Theapparatus of claim 19, further comprising: a shrink tube forshrink-tubing the probe and the signal cable; wherein the probecomprises: a center conductive probe needle; a dielectric layersurrounding the center conductive probe needle; a conductive guard layersurrounding the dielectric layer; and a sleeve surrounding theconductive guard layer; wherein the signal cable comprises: a centersignal conductor; a dielectric layer surrounding the center signalconductor; a conductive dispersion/guard layer surrounding thedielectric layer; and a sleeve surrounding the conductivedispersion/guard layer; and wherein the center conductive probe needleof the probe is disposed side by side with and electrically connects tothe center signal conductor of the signal cable, the dielectric layer ofthe probe is disposed side by side with and connects to the dielectriclayer of the signal cable, the conductive guard layer of the probe isdisposed side by side with and electrically connects to the conductivedispersion/guard layer of the signal cable, and the sleeve of the probeis disposed side by side with and connects to the sleeve of the signalcable.
 21. The apparatus of claim 20, wherein the probe furthercomprises a second dielectric layer, and the signal cable furthercomprises a second dielectric layer, wherein the second dielectric layerof the probe is disposed side by side with and connects to the seconddielectric layer of the signal cable.